IEEE 802.11 is a set of media access control (MAC) and physical layer (PHY) specification for implementing wireless local area network (WLAN) communication, called WiFi, in the unlicensed (2.4, 3.6, 5, and 60 GHz) frequency bands. The standards and amendments provide the basis for wireless network products using the WiFi frequency bands. An enhanced distributed channel access (EDCA) protocol is used in WiFi networks as a channel contention procedure for wireless devices to gain access to the shared wireless medium, e.g., to obtain a transmitting opportunity (TXOP) for transmitting radio signals onto the shared wireless medium. When one device wins the medium contention (i.e., gains the TXOP), all other devices back off from using the medium to allow frame exchange between a pair of devices during the TXOP. This simple CSMA/CA with random back-off contention scheme and low cost ad hoc deployment in unlicensed spectrum have contributed rapid adoption of WiFi systems in the past 30 years.
Today, WiFi devices are over-populated. Dense deployment has led to significant issues such as interference, congestion, and low throughput. High bandwidth applications (e.g., video streaming) also demand better performance from WiFi systems. Limited new spectrum are unable to meet the demand. However, the development of WiFi so far focus on increasing physical rate to achieve higher spectral efficiency, but not higher area throughput to achieve spatial efficiency. Area throughput/average throughput per STA is a key metric in TGax (Hew) in dense deployment scenarios. Therefore, WiFi must evolve in increasing the spatial efficiency to meet the new usage requirements.
Beamforming is an effective way to enhance cell edge performance. In general, beamforming can achieve higher physical rate, reduced interference to OBSS via beamformed transmission, reduced interference from OBSS via beamformed reception, and reduced delay spread. When more energy is delivered to the targeted receiver through TX beamforming, the less interference toward others. RX beamforming also mitigates the interference level. Results shown improved cell edge performance with TX or RX beamforming and less degradation in dense deployment.
A solution is sought to utilize beamforming as a way for exploring the possibility of spatial reuse to improve network capacity.